They seem to be of decent quality. So far I've only used my kit to notch random PCBs, so I can't comment on durability yet. But the occasions when these things come up are an exercise in frustration. They're incredibly unintuitive and difficult to open - I've never been able to open them without a small screwdriver. Even with a screwdriver, it's a nightmare. So it takes me over a minute to open the case so I can use the real tool for 30 seconds. As soon as you open it, you notice that the dimensions are simply placed loosely in the case. If you're not careful, they'll fall out and you'll wonder which color identifies which bit.